The instant invention relates generally to radio communication between moving vehicles of any desirable character and more particularly to a cooperative radio type anti-collision system for moving aircraft and other moving vehicles. While the invention is applicable to automobiles, trains, boats, and other vehicles traveling on the earth's surface and fixed objects the invention will be described in its application to flying aircraft for the purpose of simplicity.
With the increased volume of aircraft traffic presently operating through the airways and about the airports today the problem of possible aircraft collision is a major problem indeed even though air traffic control is generally considered to be superior. Rapid technology in the aircraft industry has led to the development of extremely large high speed jet aircraft which present problems regarding possible collision simply because of the great speeds at which they travel. Upon approaching an airport high speed jet aircraft are virtually always flying on a controlled approach course and frequently must aproach the airport under instrument control. It is possible for the other aircraft to enter the controlled zone unknowingly thereby creating a hazard to controlled aircraft operating under approach control. Since there are a great many more non-commercial type aircraft, frequently of small inexpensive variety, it is quite obvious that non-commercial aircraft present a hazard of possible collision that is aggravated simply by the number of aircraft that may be operating in the vicinity of an airport.
There is a need for aircraft to be capable of identifying a potential collision course with other aircraft regardless of the type or size of aircraft involved in order that evasive maneuvering may be timely accomplished in order to prevent collision with other aircraft operating in the area. It is desirable that all aircraft at least have sufficient radio gear for transmission of a signal in order that other aircraft operating nearby may receive the transmitted signal and locate the other aircraft. In the event the proximity, range, and direction of flight of the other aircraft indicate a possible collision hazard the aircraft receiving the transmitted signal may take evasive action and maneuver to prevent a possible collision.
When the wide variations in operating speeds and operating characteristics are considered carefully it becomes apparent that distance between operating aircraft becomes a relatively unimportant factor while the factor time takes on a more dominant character. For example two high speed aircraft might be several miles apart and yet because of their great speed the time to possible collision may be relatively short while two slow flying aircraft may be relatively close together and the time to possible collision might be relatively long. Also the angle at which the aircraft are approaching one another represents a factor in determining the time to possible collision. It is desirable that an anti-collision radio system be capable of determining the time to possible midair collision regardless of the relative headings and speeds of the aircraft involved.
A number of aircraft control systems are presently employed most of which utilize radar in order to locate other aircraft operating in the area. Radar direction finding equipment of ordinary sophistication has limited accuracy when considering the parameters required for aircraft anti-collision systems. The radar equipment must measure the aircraft location, the aircraft rate of position change, as well as comparing the altitude of other aircraft operating in the area. When radar anti-collision systems are provided with sufficient sophistication in order to provide the accuracy required such systems are of such extreme expense that all but the most expensive of aircraft are eliminated.
Cooerative type radio collision avoidance systems have also been developed but the degree of electrical or electronic sophistication of such systems frequently require relatively complex and expensive radio equipment in order to provide a sufficiently sensitive and reliable and fast acting system for the service required. Moreover, cooperative aircraft anti-collision systems frequently require radio gear that is extremely heavy thereby virtually eliminating small private aircraft having a limited weight carrying capacity. Private aircraft, therefore, constituting the major problem with respect to collision avoidance, would not ordinarily be provided with collision avoidance type radio gear thereby rendering the system ineffective for most private aircraft.